The invention relates to a piston, especially a cooling channel piston, of an internal combustion engine.
A cooling channel piston of an internal combustion engine is known from U.S. Pat. No. 6,155,157 which consists of exactly two parts. These parts are an upper part which has a radially peripheral ring zone and a piston head combustion bowl. A lower part is provided as a second part which accommodates the piston skirt and the piston-pin bore. At the lower edge of the ring zone and at the lowest apex of the piston head combustion bowl there are two radially peripheral joining webs on the upper part which correspond in position and extension to two joining webs on the lower part. These two parts, which can be manufactured separately from each other, are solidly joined to each other by means of a joining process which is a friction-welding process. Afterwards, a single-piece cooling channel piston is provided which can be installed into the internal combustion engine, if necessary after it has been fine machined.
In this cooling channel piston known from U.S. Pat. No. 6,155,157 both the upper part and the lower part are shaped such that after the joining process, together with the mating joining points, they form a cooling channel lying behind the ring zone to circulate cooling medium. To this end, it is necessary to place the inward lying joining point very close to the outward lying joining point which is located in the vicinity of the ring zone so that the cooling channel in the piston head can be formed thereby. However, this has the disadvantage that support for the piston head can no longer be optimally ensured, in particular with respect to the injection and ignition pressures found in modern internal combustion engines.
Therefore, it is desirable to refine a generic piston, specifically a cooling channel piston, in such way that it has improved properties with respect to its strength and long-term stability.